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The HAO-NOAO-SMARTS Southern HK Project. Travis Metcalfe. Population as context. Population as context. B ö hm-Vitense (2007). Solar and stellar activity cycles. Magnetic regions on the Sun are bright in Mg II (UV) and Ca II (optical)

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Southern HK Project

Travis Metcalfe


Population as context

Böhm-Vitense (2007)


Solar and stellar activity cycles

  • Magnetic regions on the Sun are bright in Mg II (UV) and Ca II (optical)
  • Measure ratio of total emission in line cores to flux in the wings
  • Use disk-integrated time series measurements to track magnetic cycles

frequency shifts

Salabert et al. (2004)

Frequency shifts
  • Solar p-mode shifts first detected in 1990, depend on frequency and degree
  • Even the lowest degree solar p-modes are shifted by the magnetic cycle
  • Unique constraints on the mechanism could come from asteroseismology

Libbrecht & Woodard (1990)

hd 2151 b hydri
HD 2151 (b Hydri)

Metcalfe et al. (2007)

  • Reanalysis of archival IUE data, including more recent observations
  • Asteroseismic data from 2000 (just past maximum) and 2005 (near minimum)
  • Mean shift: 0.1 + 0.4 mHz, individual n=18 frequency shift: 0.17 + 0.62 mHz




Southern HK project

  • Small telescopes at CTIO run by SMARTS partners: Yale, GSU, STScI, et al.
  • Service observing 2-3x per month using RC Spec with R ~ 2500 at Ca HK
  • Monitor bright southern asteroseismic targets for stellar activity variations

Metcalfe et al. (2009, arXiv:0909.5464)


HD 17051 (i Hor)

  • Shortest measured stellar activity cycle in a solar-type star: 1.6 years
  • Sampling permits some indication of the rotation rate: ~3x solar (8.5 days)
  • Asteroseismology in 2007 (near maximum), repeat at minimum in late 2013?

Metcalfe et al. (2010)


Short activity cycles

  • Confirm ~2.5 year cycle in HD 76151 from Mount Wilson survey
  • Cycle in HD 22049 (e Eri) may be shorter than the ~5 year MWO result
  • Irregular short period variations in HD 30495, as in Mount Wilson

Pcyc > 220 days

(270, 350, 490)

Garcia et al. (2010)

CoRoT: HD 49933

  • Solar pattern of frequency and amplitude changes observed in HD 49933
  • Frequency dependence of shifts also similar to (but larger than) solar
  • Second 150 day run by CoRoT begins October, with HK from SMARTS

Salabert et al. (2011)


Kepler: the NOT sample

Chaplin et al. (2007)

  • Two proposed scalings for frequency shifts as a function of spectral type
  • HD 49933 shows larger than solar shifts, supports Dziembowski scaling
  • Several dozen Kepler targets being monitored in Ca HK from NOT

Metcalfe et al. (2007)

Karoff et al. (2009, 2010)


Future prospects

  • Satellite missions will extend the calibration of dynamo models to many unique sets of physical conditions and to different evolutionary phases.
  • Must be coupled with long-term ground-based monitoring of stellar activity cycles from Ca HK surveys (Lowell, SMARTS, CASLEO).
  • We will eventually move beyond scaling from solar data, and use the new observations as independent tests of dynamo models.